This invention relates to ramjet engines operable over a range of supersonic speeds. More specifically, this invention relates to variable-geometry ramjet engines capable of oepration in the Mach 3 to 12 speed range. This variable-geometry ramjet engine configuration matches the conflicting requirements of a supersonic inlet, a combustor, and a nozzle to provide a sophisticated supersonic ramjet engine which is efficient, minimizes performance compromises, and is structurally, uncomplicated.
It is well known in the prior art to provide axisymmetric external-plus-internal compression inlets for use on supersonic engines. Such inlets compress the flow by a series of oblique shocks to provide a high inlet total pressure recovery. Automatic scheduling of the inlet cowl position to accommodate various flight speeds is well within the state of the art.
The selection of a burner geometry is a compromise of the various area ratio schedules which can be achieved within the geometrical limitations of a practical engine scheme. At low Mach numbers, the combustor entrance area or inlet throat area and the burner area ratio are increased. The nozzle, having an increasing area ratio with increasing Mach number, is required to provide the proper expansion of the hot engine exhaust stream.
I have found that I can incorporate these requirements into a simple ramjet engine by a single movable element, namely the translatable cowl. With my invention, the engine geometry has not been compromised to the extent that the attractive high-speed performance is seriously degraded. I have found that a ramjet engine can be provided to operate over a wide Mach number range without severely compromising the conflicting requirements of the inlet, burner, and nozzle at the various flight speeds. Further, this engine is capable of varying the basic engine design parameters with a single moving component, thus providing a practical engine construction.